1. Field of the Invention
The present invention generally relates to electronic apparatuses which employ optical fibers as optical signal transmission paths and carry out information processing and communication of various types.
2. Description of the Related Art
As the amount of data transmission has dramatically increased due to the spread of the Internet and other communication devices, there has been a demand for optical multiplexing communication apparatuses having a larger capacity for data transmission. Therefore, it is necessary to develop a high performance apparatus having a high density and capable of transmitting a large amount of information at a high speed.
In response to this demand, multiplexing apparatuses employing a TDM (Time division Multiplexing) system have been developed. In the TDM system, electrical signals are multiplexed on the time base. However, super high-speed signals, such as 10 Gb/s signals, have very short time intervals between signals, and the TDM system has almost reached the limit of today""s signal transmission technique in terms of speed.
Meanwhile, in a communication system which employs optical fibers as signal transmission paths, super high-speed signals, such as 10 Gb/s signals, cannot be transmitted through conventional 1.3 xcexcm optical fibers over a long distance, due to the optical wavelength dispersion. This problem can be solved by using high performance optical fibers, such as 1.55 xcexcm DSFs (Dispersion Shifted Fibers), for restricting wavelength dispersion. However, a large expense is required for laying such optical fibers.
In view of these facts, apparatuses which employ a WDM (Wavelength Division Multiplexing) system are becoming the mainstream to solve the above-mentioned problems and to achieve high-density and large-volume information transmission.
In the WDM system, optical signals are multiplexed on the optical wavelength axis. At present, 45 wavelengths is standardized by the ITU standards. Accordingly, at the rate of 10 Gb/s, a large volume (10 Gxc3x9745=450 G) of information can be transmitted through one optical fiber. In the future optical multiplexing communication system, 45 waves can be handled both on the multiplexing side and the separation (or demultiplexing) side. Therefore, as many as 90 optical fibers may be employed in one system. This trend toward a larger number of optical fibers is continuing.
An optical multiplexing communication apparatus basically has a transmitting side (multiplexing side) and a receiving side (separation side). The transmitting side comprises a transmitting unit (OS), an ATT unit, and an optical MUX. The ATT unit adjusts and optimizes the levels of optical signals from the OS. The optical MUX then multiplexes optical signals having different optical wavelengths xcex1 to xcexn, and then transmits the multiplexed optical signals. When transmitting optical signals over a long distance, an optical AMP unit is employed, where necessary, to directly amplify the optical signals.
The receiving side comprises an optical DMUX unit, an ATT unit, and a receiving unit (OR). The optical DMUX unit separates the individual optical signals in accordance with the different optical wavelengths xcex1 to xcexn. The ATT unit then adjusts and optimizes the level of each optical signal, and the OR outputs separated signals. On the receiving side, an optical AMP unit for directly amplifying received optical signals is also employed, where necessary.
Two optical fibers each provided with an optical connector can be detachably connected to each other. The two optical connectors are brought into contact facing each other, thereby optically connecting the corresponding optical fibers to each other.
FIG. 29A is a perspective view of a first example of an optical connector adapter. This optical connector adapter 1 has flanges 2 in the middle, and is attached to an L-shaped attachment metal fitting 3 with attaching screws 4. The attachment metal fitting 3 is secured to desired positions on the apparatus.
Optical connectors are inserted into both ends of the optical connector adapter 1, and the ferrules of the optical connectors are pressed and optically coupled to each other inside a sleeve (not shown). SC-type optical connectors can be inserted into and connected to both ends of the optical connector adapter 1.
FIG. 29B is a perspective view of the optical connector adapter 1 with an SC-type optical connector 5-1 inserted into one end and another SC-type optical connector 5-2 which is yet to be inserted into the other end. A single-core optical fiber 6 is introduced into each of the optical connectors 5-1 and 5-2. When inserted, the SC-type optical connectors 5-1 and 5-2 are locked to the optical connector adapter 1 in an insertion position. The SC-type optical connectors 5-1 and 5-2 can easily be released from the optical connector adapter 1.
FIG. 30A is a perspective view of a second example of an optical connector adapter. This optical connector adapter 7 has flanges 8 in the middle, and is attached to the L-shaped attachment metal fitting 3 with the attaching screws 4. The attachment metal fitting 3 is secured to desired positions on the apparatus.
Optical connectors are inserted into both ends of the optical connector adapter 7, and the ferrules of the optical connectors are pressed and optically coupled to each other inside a sleeve (not shown). An SC-type optical connector can be inserted into and connected to one end of the optical connector adapter 7, and an FC-type optical connector can be inserted into and connected to the other end of the optical connector adapter 7.
FIG. 30B is a perspective view of the optical connector adapter 7 with an SC-type optical connector 5 inserted into one end and an FC-type optical connector 9 which is yet to be inserted into the other end. A single-core optical fiber 6 is introduced into each of the optical connectors 5 and 9. When inserted, the SC-type optical connector 5 is locked to the optical connector adapter 7 in an insertion position. The SC-type optical connector 5 can easily be released from the optical connector adapter 7. The FC-type optical connector 9 is attached to the optical connector adapter 7 by tightening a ring nut 12 to a screw 11 formed around the optical connector adapter 7, and is detached by loosening the ring nut 12.
FIG. 31A is a perspective view of a third example of an optical connector adapter. This optical connector adapter 14 has flanges 15 in the middle, and is attached to the L-shaped attachment metal fitting 3 with the attaching screws 4. The attachment metal fitting 3 is secured to desired positions on the apparatus.
Optical connectors are inserted into both ends of the optical connector adapter 14, and the ferrules of the optical connectors are pressed and optically coupled to each other inside a sleeve (not shown). An SC-type optical connector can be inserted into and connected to one end of the optical connector adapter 14, and an ST-type optical connector can be inserted into and connected to the other end of the optical connector adapter 14.
FIG. 31B is a perspective view of the optical connector adapter 14 with an SC-type optical connector 5 inserted into one end and an FC-type optical connector 16 which is yet to be inserted into the other end. A single-core optical fiber 6 is introduced into each of the optical connectors 5 and 16. When inserted, the SC-type optical connector 5 is locked to the optical connector adapter 14 in an insertion position. The SC-type optical connector 5 can easily be released from the optical connector adapter 14. The ST-type optical connector 16 is attached to the optical connector adapter 14 by rotatably covering a protrusion 17 on the optical connector adapter 14 with a ring 19 having a helix in a bayonet-like manner.
FIG. 32 is a perspective view of a conventional optical multiplexing communication apparatus. This optical multiplexing communication apparatus 21 is attached between a pair of support pillars 22, and has two printed board shelves 24 disposed one above the other. A number of printed board units 23 are inserted and plugged in the printed board shelves 24. The upper printed board shelf 24 is a multiplexing unit, while the lower printed board shelf 24 is a separation unit. Sixteen printed board units are inserted into each of the printed board shelves 24. The number of printed board shelves 24 can be increased if there is an increase in the number of communication lines.
In FIG. 32, the leftmost one of the printed board units 23 is pulled out of each of the printed shelves 24. The printed board units 23 are mounted with optical signal processing circuits, electric/optical signal conversion devices, optical/electrical conversion devices, and others, which are not shown in the figure to avoid unnecessary complexity.
It is necessary to connect external optical fibers 25 and internal optical fibers 6 to each of the printed board units 23, and therefore a plurality (four in FIG. 32) of optical connector adapters are attached to the front side of a surface of each printed board unit 23 with attachment metal fittings.
A guide board 26 for guiding air upward from the front side to the rear side is disposed above each of the printed board shelves 24. The guide board 26 is used to discharge the air heated by the circuit devices during an operation. The lower surface of the guide board 26 guides and discharges the heated air to the rear side, and the upper surface guides and sucks in cool air from the outside. The inclination of the guide board 26 also forms a space between the bottom surface of the upper printed board shelf 24 and the top surface of the lower printed board shelf 24.
The air ventilation can be selectively carried out by natural convention depending on temperature variations or by an electric fan (not shown) disposed on or under the printed board shelves 24. The optical fibers 25, including the optical fibers between the printed board units 23, the optical fibers between the printed board shelves 24, the optical fibers connected to external lines, are all introduced to the front side via the rear side and upper side of each of the guide boards 26, as shown in FIG. 32.
Since each of the optical fibers 25 requires some extra length depending on the intended use of demand, the extra length 27 is wound and disposed on the guide board 26. A positioning member (not shown) secures the extra length 27 of each optical fiber 25 to maintain an orderly state.
Each of the printed board units 23 is provided with the same number of optical connector adapters 1, as well as the circuits corresponding to the number of lines required. The optical connectors of the external optical fibers 25 can be attached to and detached from the optical connector adapters 1 according to changes in the number of lines.
When attaching or detaching the optical connectors, it is necessary to pull out the printed board units 23 and put them back to their original positions, as shown in FIG. 32.
FIG. 33 is a sectional side view of the optical multiplexing communication apparatus 21. In this figure, the printed board units 23 are inserted into the printed board shelf 24, and the internal optical fibers and their optical connectors are not shown for ease of explanation. Only the optical connectors 28 of the external optical fibers 25 are shown connected to the optical connector adapters 1.
Guide portions (not shown) for guiding the printed board units 23 forward and backward, and air holes (not shown) for moving air in the vertical direction are formed on the upper and lower surfaces of the printed board shelf 24. In FIG. 33, the left side is the front side of the apparatus 21, and the right side is the rear side of the apparatus 21. A backboard 31 that is a printed board provided with backboard connectors 32 is attached to the rear side of the printed board shelf 24.
Each of the printed board units 23 has a front plate 35 on the front side, insertion members 36 at the top and bottom on the front side, a stopper 37 at the bottom halfway to the rear side, and a printed board unit connector 38 on the rear side. When the printed board units 23 are inserted into the printed board shelf 24, the printed board unit connectors 38 are plugged in the backboard connectors 32.
On the upper surface of the guide board 26, the extra lengths 27 of the external optical fibers 25 are wound and placed from the rear side to the front side. The external optical fibers 25 are then introduced into the printed board units 23 on the front side, and are bundled by bundling bands 39 which are secured to the front sides of the printed board units 23.
In FIG. 33, four external optical fibers 25 are connected to the optical connector adapters 1, but if the number of lines increases or decreases or the lines are changed, it is necessary to attach more of the optical connectors 28 to the optical connector adapters 1, or to detach some of the optical connectors 28 from the optical connector adapters 1.
The attachment and detachment of the optical connectors 28 are carried out by manipulating the insertion members 36, as shown in FIG. 34. Here, the stopper 37 of each of the printed board units 23 is stopped by a metal fitting on the front side of the printed board shelf 24, and the backboard connector 32 and the printed board unit connector 38 become electrically disconnected. The wound extra lengths 27 are stretched at the same time, and the bundling bands 39 are detached or reattached.
However, the above procedures cause inconvenience, because all the operations have to stop for the attachment and detachment of the connectors. To solve this problem, flexible portions 43 are formed diagonally to the front plate 42 of a printed board unit 41, as shown in FIG. 35. The optical connector adapters 1 are directly attached to the flexible portions 43, and the internally connected optical connectors 5 are also connected to the flexible portions 43.
By connecting and detaching a desired external optical connector 28 as shown in FIG. 35 depending on a increase or decrease of the number of lines, the necessary procedures can be carried out without pulling the printed board unit 41 out of the printed board shelf, without stopping the operations of the circuits, and without pulling the extra lengths 27 of the optical fibers 25.
The flexible portions 43 are formed in the middle of the front plate 42 and the optical connector adapters 1 are attached to the flexible portions 43. With this configuration, spaces required for the optical connectors protruding from the front side or for the bent portions of the optical fibers can be greatly reduced.
As shown in FIG. 35, a larger number of optical connector adapters 1 result in compressing the circuit mounting area of the printed board unit 41 due to the flexible portions 43 of the front plate 42 lined in the depth direction.
To avoid such a problem, another type of optical multiplexing communication apparatus shown in FIG. 36 has been developed. In this figure, only two printed board units 45 in different positions are shown, but it should be understood that there are some others inserted into the printed board shelf.
The printed board unit 45 on the right side in the figure is denoted by 45-1, the other one on the left side is denoted by 45-2. The printed board unit 45-1 is inserted into the printed board shelf, so that the printed board unit connector 38 is insert-connected to the backboard connector 32.
Each of the printed board units 45-1 and 45-2 is made up of a main printed board 46 and a sub printed board placed in parallel with the main printed board 46. The sub printed board 47 is rotatably supported by a shaft (not shown) at the upper corner on the front side. On the rear side, a guide member 48 is provided to the main printed board 46, and the rim of the rear side of the sub printed board 47 is engaged with the guide portion 48. An arcuate guide 49 (indicated by broken lines) formed with the rotation shaft as its center is disposed below the sub printed board 47. The rotation of the arcuate guide 49 is restricted so that the sub printed board 47 is not completely separated from the main printed board 46.
A screw 52 is attached to a lower portion of the front plate of each sub printed board 47, and secures the sub printed board 47 to the front plate of the main printed board 46, as indicated by the printed board unit 45-1 in FIG. 36. By loosening the screw 52, the sub printed board 47 can be pulled around at a rotation angle xcex8 to the position indicated by 45-2. To allow such rotational movement, each main printed board 46 and sub printed board 47 are connected by a flexible flat cable 53 having a sufficient length.
An optical circuit device 55 is mounted on each sub printed board 47, and the external optical fibers 25 to be connected to the optical circuit device 55 are introduced from the upper rear side of the printed board shelf 24 to the upper front side, with the extra length 27 being disposed on the guide board 26.
The optical connector adapters 1 are attached to the attachment metal fittings 3 arranged on the sub printed board 47, and the internal optical fibers 6 are connected to the external optical fibers 25 via the optical connector adapters 1.
By rotatively moving the sub printed board 47 to the position indicated by 45-2, attachment and detachment of the optical connectors 28 of the external optical fibers 25 can be carried out without pulling the printed board unit 45 out of the printed board shelf 24. Thus, increasing and reducing the number of lines can be carried out, with the backboard connectors 32 remaining electrically connected to the printed board units 45.
FIG. 37 shows yet another type of optical multiplexing communication apparatus of the prior art. In order to allow more optical fibers 25 to printed board units 57, optical connector adapters 58 that are small in size are provided. Mu-type optical connectors can be connected to both ends of each of the optical connector adapters 58, so that high-density connection can be achieved.
With this structure, a large number of lines can be connected to one printed board unit 57 at once. However, to avoid bundled optical fibers 25 protruding from the front plate, it is necessary to form a notch 59 in the upper portion of the printed board shelf 24.
The above examples of optical multiplexing communication apparatus of the prior art have the following problems.
In the structure shown in FIGS. 32 to 34, when the optical connectors 28 of external optical fibers are attached or detached, the printed board units 23 are always electrically disconnected from the backboard 31. If a large number of optical connector adapters 1 are employed to increase the number of lines to be introduced into each printed board unit 23, the optical connector adapters 1 occupy a large area, taking up the space of the circuits. If the optical connector adapters 1 are arranged in the thickness direction, attachment and detachment of the optical connectors 28 become difficult, and each printed board unit 23 becomes thicker. Therefore, the number of lines to be introduced is limited. Also, it is necessary to have the extra length 27 for each optical fiber 25 to be introduced. The extra length 27 needs to be stretched when the printed board unit 23 is pulled out, and needs to be returned to its original position when the printed board unit 23 is inserted back into the printed board shelf 24. Furthermore, the extra length 27 is disposed on the guide board 26, and therefore the process needs to be carried out in the restricted space between two printed board shelves 24. This makes the whole procedures even more troublesome.
In the structure shown in FIG. 35, the number of flexible portions 43 becomes limited, because a large space is required for disposing the flexible portions 43 in the depth direction. Arranging the optical connector adapters 1 horizontally in line on the front side is problematic, considering the difficulty in attaching and detaching the optical connectors 28 and the thickness of each printed board unit 41. The problem of the extra portion 27 of each optical fiber 25 also remains unsolved in this structure.
In the structure shown in FIG. 36, each of the printed board units 45 consists of the main printed board 46 and the sub printed board 47, resulting in a large thickness. Rotating the sub printed board 47 is also a complicated procedure. To employ a large number of optical connector adapters 1 requires a large area on each sub printed board 47. Therefore, the number of optical connector adapters 1 still becomes limited, and it is not easy to attach and detach the optical connectors 28. The problem of the extra length 27 of each optical fiber 25 also remains unsolved in this structure.
In the structure shown in FIG. 37, it is possible to introduce a large number of optical fibers 25 into each printed board unit 57. However, attaching the optical connectors to the small, high-density optical connector adapters 58 requires special implements. Besides the problem of the extra length 27 of each optical fiber 25, the notch 59 formed for introducing the optical fibers 25 causes yet another problem. Since the optical fibers 25 are not made of a conductive material, the notch 59 is deemed as a space from an electric point of view. Electromagnetic waves having a wavelength corresponding to the size of the space can pass through the space, thereby causing electromagnetic interference to internal and external circuits.
A general object of the present invention is to provide an electronic apparatus in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an electronic apparatus in which a large number of optical connectors of optical fibers are connected and arranged neatly in a small space. Also, attaching and detaching external optical connectors can be easily carried out in this apparatus.
The above objects of the present invention are achieved by an electronic apparatus which comprises an optical connector adapting unit including a plurality of optical connector adapters to which optical connectors of external optical fibers are connected. The optical connector adapters are diagonally arranged on the front side of the apparatus. The optical connectors can be attached to and detached from the optical connector adapters in the diagonal direction on the front side of the apparatus.
Since the optical connector adapters are disposed diagonally from the front surface of the apparatus, the depth of the space occupied by the optical connector adapting unit can be made shorter than that in the prior art. Thus, the total area occupied by the apparatus can be made smaller.
By diagonally arranging the optical connector adapters, all the optical connector adapters can be seen in the front view. In such a configuration, all the optical connectors can be easily recognized, i.e., all the lines can be easily recognized. Thus, wrong connections can be effectively prevented.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.